An anti-hail shock wave generator or cannon is known in the art from U.S. Pat. No. 3,848,801. In such a device, a shock wave is generated by detonating an explosive mixture of combustible gas and air in a combustion chamber having an upper orifice. A conical barrel is fit over the upper orifice and directs the shock wave resulting from the explosion upwardly to the sky. By firing the generator at regular intervals (e.g. less than 25 seconds, and usually every 8 to 14 seconds), a succession of shock waves are created which disrupts the internal microstructure of the clouds to prevent the formation of hail nuclei within a small area (typically a 500 m radius) over the generator. It is believed that transport of positive ions from ground level to cloud level by the succession of shock waves is largely responsible for the disruption of the formation of hail nuclei.
By using the known device, crop damage due to hail has been known to be completely eliminated or at least significantly reduced without any adverse environmental effects, however, to achieve good results, special care must be taken to operate the device properly starting about 15-30 minutes before a hail storm in order to disrupt sufficiently the hailstone formation process. By operating the device at a faster firing rate (less than 8 seconds between ignitions), the combustion chamber and the barrel are subjected to more mechanical and temperature stress, and more fuel is consumed.